Method and apparatus for alignment of components

ABSTRACT

The present invention relates to a method for measuring the relative positions of a first component ( 1 ) and a second component ( 2 ), said method comprising: mounting a first measurement unit ( 6 ) on a housing ( 7 ) forming part of said first component ( 1 ) by means of a first bracket ( 21 ), said first measurement unit ( 6 ) being rotatably arranged in relation to said first bracket ( 21 ) and defining a first rotational axis; and mounting a second measurement unit ( 8 ) on a further housing ( 9 ) forming part of said second component ( 2 ) by means of a second bracket ( 26 ), said second measurement unit ( 8 ) being rotatably arranged in relation to said second bracket ( 26 ) and defining a second rotational axis. The invention also comprises measuring, in a first state of operation of said first component ( 1 ) and said second component ( 2 ), the relative position of said first component ( 1 ) in relation to said second component ( 2 ) by detecting the position of said first axis and by detecting the position of said second axis; providing measurement values corresponding to the positions of said first rotational axis and said second rotational axis, measuring, in a second state of operation of said first component ( 1 ) and said second component ( 2 ), the relative position of said first component ( 1 ) in relation to said second component ( 2 ) by detecting the position of said first axis and by detecting the position of said second axis; and obtaining information related to the relative positions of said first component ( 1 ) in relation to said second component ( 2 ) based on the measurements made in said first state of operation and the measurements made in said second state of operation. The invention also relates to an apparatus for such measurements.

TECHNICAL FIELD

[0001] The present invention relates to a method for measuring therelative positions of a first component and a second component. Theinvention can for example be applied in alignment of components, forexample in the form of machines such as engines, pumps or couplings.

[0002] The present invention also relates to an apparatus for measuringthe relative positions of a first component and a second component.

BACKGROUND OF THE INVENTION

[0003] In various fields of technology there is a need for correctalignment of different components and machines in relation to eachother. For example, during operation of large engines, pumps and similarequipment, it is essential that an output shaft of a propelling unit,for example in the form of an engine, is correctly aligned with respectto an input shaft of a propelled unit, for example in the form of apump. In this manner, the output power of the engine can be transferredvia the rotational movement of the engine shaft to the input shaft ofthe pump in an optimal manner. Any misalignment of the two shafts mayresult in a poor efficiency and an increased risk for wear and damage tothe engine or the pump.

[0004] Consequently, in the above-mentioned field of technology, thereis a demand for correct alignment of the engine output shaft in relationto the input shaft of the pump. In this regard, it should be noted thatthe two shafts may present alignment errors of generally two differentkinds. To be precise, the shafts may be disposed at a certain angle withrespect to each other, which is referred to as an angular error, i.e. a“horizontal angular error” and a “vertical angular error”. Secondly,even though the shafts may be parallel to each other, they may beslightly displaced with respect to each other so that they extend alongtwo separated directions, i.e. in a parallel manner. This is referred toas “horizontal offset” and “vertical offset”. If these errors exceedpredetermined limit values, it can be assumed that the shafts, and theircorresponding machines, are poorly aligned with reference to each other.

[0005] Consequently, there is a general demand for systems and methodsfor aligning various pieces of machinery comprising rotatable shafts.Such systems and methods may be used for engines and pumps and similarequipment. Generally, they may be used in power plants, chemical plantsand oil refineries, in particular in applications which comprise highspeed or in applications comprising expensive, process critical machineswhich are necessary to align.

[0006] According to prior art, alignment of two rotatable shafts of twomachines can be carried out by means of a measuring apparatus whichcomprises a first measuring unit arranged for mounting on a firstmachine and comprising a light source for generation of light radiationin the direction towards a second measuring unit arranged for mountingon a second machine and also comprising a second light source forgeneration of light radiation in the direction towards the firstmeasuring unit. Furthermore, each of the measuring units comprises adetection device for emitted light radiation. By means of thisapparatus, the alignment of the two shafts of the machines can beinvestigated.

[0007] The above-mentioned type of measuring equipment is intended to beused when the relevant machines are standing still, i.e. when they arerelatively cold and not in use for the moment.

[0008] However, it should be noted that in many applications, thealignment between an engine and a pump, for example, may change as thesemachines are started and operated and gradually become hot, i.e. fromcold and shutdown to normal operation. For example, the alignment mayvary depending on the operating temperature of the machines. Thealignment may also vary depending on changes in discharge pressure (ifalignment is carried out on a pump or a compressor). Also, piping strainin the shafts may cause changes in alignment between cold and hotoperating conditions.

[0009] The change in alignment between a cold and a hot condition mayalso be influenced if the relevant machines operate in parallel, or ifany changes in electrical loading or rotational forces should occurduring operation.

[0010] Consequently, there are thermal factors and other parameterswhich affect the alignment of the machines. In particular, as explainedabove, a problem exists in that a correct alignment of a still-standingmachine may not necessarily correspond to a correct alignment of thesame machine when it is operated. This means that it will be necessaryto carry out some type of adjustments in order to compensate for thefact that alignment changes will occur between a cold and a hotcondition.

[0011] A previously known system for measuring the difference inalignment from a cold start condition to a hot operating condition ismanufactured by the company Prüftechnik and comprises two unitsconstituting combined transmitters and detectors to be mounted on afirst, stationary machine, suitably on a bearing housing on said firstmachine. The transmitters comprise laser light sources. Correspondingprisms are mounted on a second, moveable machine which is intended to beadjusted so as to obtain correct alignment.

[0012] The lasers are set up, one in the vertical plane and one in thehorizontal plane. The horizontal head must point toward 3 o'clock, andthe vertical head must point toward 12 o'clock. After this set up, eachprisms have to be aligned to reflect its corresponding laser beam intothe corresponding detector. The units comprising the transmitters anddetectors are connected to a control unit which transmits the data to acomputer, for example of the PC type. A particular software program isused to trend the data streaming from the transmitters and detectors.This results in measuring information in the form of graphs indicatingpositional changes during operation of the relevant machines.

[0013] A disadvantage with this previously known system relates to thefact that it comprises four different units which must be mounted andadjusted before measurements can be carried out. This means that thissystem is relatively complicated and time-consuming to set up and use.In fact, the setup of this previously known system takes an experienceduser about two hours per coupling to set up. This does not include thetime spent by the operator programming alignment formulas into thecomputer. The system also requires high amounts of training to be usedproperly as well as extensive knowledge of computer use for an operator.It is also relatively expensive.

[0014] A further disadvantage with this previously known system relatesto the fact that a separate graph is required from each alignmentparameter to be monitored. This means that on a typical single couplingmeasurement, four different graphs are required. This results in atime-consuming operation as well as a time-consuming and complicatedevaluation of the measurement data.

[0015] Another previously known system is disclosed in U.S. Pat. No.5,077,905, which teaches a laser alignment mount assembly comprising afirst measuring unit and a second measuring unit. This known assembly isadapted for alignment of two coupled shafts during a first operationalcondition and a second operational condition. By means of the system, aninitial “zeroing” of the equipment is carried out in said firstoperational condition by setting a laser beam in coincidence with atarget. In this manner, a zero reference is determined. When the coupledshafts are in said second operational condition, a “re-zeroing” is madeby displacing one of the measuring units so as to be aligned with thetarget and by mechanically measuring the positional change resultingfrom the movement off the zero reference point when the system entersthe second operational condition.

[0016] A disadvantage with the system shown in U.S. Pat. No. 5,077,905relates to the fact that it relies on both a laser measurement systemand a mechanical measurement device to gather alignment change data,i.e. for providing the result of the above-mentioned “re-zeroing”. Also,the “re-zeroing” is carried out following a mechanical manipulation of amounting bracket.

SUMMARY OF THE INVENTION

[0017] An object of the present invention is to provide a method andapparatus, respectively, by means of which an improved measurement ofthe changes in relative positions of two components, in particular forcarrying out shaft alignment of co-linear centers of rotation of two ormore shafts, is accomplished. A particular object is to providealignment during normal (hot) operating conditions.

[0018] The above-mentioned object is accomplished by means of a methodfor measuring the relative positions of a first component and a secondcomponent, said method comprising: mounting a first measurement unit ona housing forming part of said first component by means of a firstbracket, said first measurement unit being rotatably arranged inrelation to said first bracket and defining a first rotational axis; andmounting a second measurement unit on a further housing forming part ofsaid second component by means of a second bracket, said secondmeasurement unit being rotatably arranged in relation to said secondbracket and defining a second rotational axis. The method according tothe invention further comprises: measuring, in a first state ofoperation of said first component and said second component, therelative position of said first component in relation to said secondcomponent by detecting the position of said first axis and by detectingthe position of said second axis; providing measurement valuescorresponding to the positions of said first rotational axis and saidsecond rotational axis, measuring, in a second state of operation ofsaid first component and said second component, the relative position ofsaid first component in relation to said second component by detectingthe position of said first axis and by detecting the position of saidsecond axis; and obtaining information related to the relative positionsof said first component in relation to said second component based onthe measurements made in said first state of operation and themeasurements made in said second state of operation.

[0019] The above-mentioned object is also accomplished by means of anapparatus for measurements of the relative positions of a firstcomponent and a second component by means of a first measurement unitand a second measurement unit, said apparatus comprising: a firstbracket for mounting the first measurement unit on a housing formingpart of said first component; a second bracket for mounting the secondmeasurement unit on a further housing forming part of said secondcomponent; each measurement unit being fixedly mounted on a rotatableelement which is arranged in each corresponding bracket, therebydefining a first rotational axis for the first measurement unit inrelation to the first bracket and a second rotational axis for thesecond measurement unit in relation to the second bracket. According tothe invention, said measurement units are adapted for measuring, in afirst state of operation of said first component and said secondcomponent, the relative positions of said first component in relation tosaid second component by detecting the position of said first axis andby detecting the position of said second axis, and for measuring, in asecond state of operation of said first component and said secondcomponent the relative positions of said first component in relation tosaid second component by detecting the position of said first axis andby detecting the position of said second axis.

[0020] An important advantage with the present invention is that itconstitutes a simple solution which is also compact and easy to operate.In particular, the system according to the invention is easy to set up,mount and break down. The invention also provides very accuratealignment with the user of relatively simple, visible laser system. Thesystem according to the invention is easy to install and easy to adjustprior to actual measurements. Furthermore, the system according to theinvention requires no particular computer programming for the operatorusing it, and consequently constitutes a user-friendly system.

[0021] A particular advantage of the invention relates to the fact thatit allows the use of measurement equipment of the same kind as usedduring normal shaft alignments at a single operating condition (normallya cold, non-operative state). The invention also allows the samemeasuring process as according to prior art to be used when carrying outthe present invention. The invention can be adapted to all measurementsunits which are available on the market today, which means that theinvention constitutes a simple and flexible solution.

BRIEF DESCRIPTION OF THE DRAWINGS

[0022] The invention will now be described with reference to a preferredembodiment and the appended drawings, in which:

[0023]FIG. 1 shows in a schematic manner an alignment set-up in whichthe present invention is used;

[0024]FIG. 2 shows an apparatus according to the present invention, in apartially assembled state; and

[0025]FIG. 3 shows how a measurement unit according to the invention canbe mounted; and

[0026]FIGS. 4a-c show how the measurement units can be moved betweenthree different position for obtaining measurement values.

PREFERRED EMBODIMENTS

[0027] The present invention will now be described, firstly withreference to FIG. 1, which shows in a schematic manner an arrangement inwhich the invention suitably can be used. Said arrangement comprises afirst machine 1 which can be constituted by an engine, the output powerof which is intended to be transferred to a second machine 2. Saidsecond machine 2 is suitably constituted by a pump or some other form ofpropelled unit, such as for example a generator. The invention is notlimited to be used with an engine and a pump, but can be implemented forall types of measurements of the relative position between a firstcomponent and a second component during various types of operationalconditions.

[0028] The output power of the engine 1 is transferred to the pump 2 viaan output shaft 3 of the engine 1, a coupling 4 and an input shaft 5 ofthe pump 2.

[0029] As mentioned initially, there is a demand for correct alignmentof the engine's 1 output shaft 3 in relation to the input shaft 5 of thepump 2. In particular, the alignment can be evaluated by determining theangular errors and offset values of the two shafts 3, 5. There is also aneed for determining whether these parameters are within predeterminedallowed limit values.

[0030] The invention is not limited to be used with any particular typeof propelling or propelled machine or other equipment. The equipment forwhich the invention is used does not itself form part of the invention.Generally, the invention can be used in any situation in which there isa demand for aligning two components arranged for transmitting power inany direction between the components. In particular, the invention isused for alignment of co-linear centers of rotation of two or moreshafts. For example, the invention can be used for alignment of machinessuch as engines and pumps. The invention can also be used in situationin which no transmission of power is intended. For example, the relativeposition between two components (for example a machine and its supportstructure) can generally be measured at different states of operation.

[0031] As explained above, the invention is particularly suitable forcooperating with many different types of known measurement units. Asindicated in FIG. 1, the invention may for example be used with a firstmeasuring unit 6 which is mounted in a certain position with respect toa housing 7 of the engine 1 during alignment of the engine 1 and thepump 2. Furthermore, the apparatus according to the invention is alsointended to be used with a second measuring unit 8 intended to bemounted in a position with respect to a housing 9 of the pump 2. As willbe described below, the invention comprises brackets for mounting themeasuring units 6, 8.

[0032] It can be noted that either one of the engine 1 and the pump 2,for example the engine 1, is stationary, i.e. it is not intended to bemoved. The other apparatus, i.e. the pump 2 in this case, is movable.The invention can thus be used for an application in which a measurementunit is mounted on a stationary apparatus and another measurement unitis mounted on a movable apparatus. However, the invention is not limitedto such applications, but can also be used with non-movable machines.

[0033] The first measurement unit 6 comprises a first light source 10,which is preferably a laser light source which is adapted for providinga first laser beam 11 directed towards the second measurement unit 8.For this reason, the second measurement unit 8 comprises a lightdetector 12 arranged for detecting any incoming light from the firstlight source 10. Furthermore, the second measurement unit 8 comprises asecond laser light source 13 for producing a further laser light beam 14intended to be directed towards the first measurement unit 6, inparticular towards further light detector 15 arranged in said firstmeasurement unit 6 and adapted for detecting any incoming light from thesecond laser light source 13.

[0034] The invention can alternatively be adapted to be used with othertypes of measurement units. For example, measurement units of the typewhich do not use laser light but some other form of light source can beused by means of the invention. The set of measurement units can beconstituted by a first measurement unit comprising a light source, whichcooperates with a second measurement unit comprising a light reflector.The reflected light is detected by means of a light detector on thefirst measurement unit. As an alternative, the detector unit may bemanually operated, i.e. it may comprise a target in the form of a numberof lines which are used by an operator for visually detecting whetherthe measurement units are aligned. As an alternative to measurementsinvolving a light source, a mechanical alignment equipment comprisingthe so-called mechanical dial indicator method, can also be used withthe invention.

[0035] The measurement units 6, 8 are mounted on the engine 1 and thepump 2, respectively, by means of a first mounting arrangement 16 and asecond mounting arrangement 17, respectively. The mounting arrangements16, 17 are indicated in a simplified and schematic manner in FIG. 1, butwill now be described in greater detail with reference to FIG. 2. Asindicated in FIG. 2, which shows an arrangement partly assembled, justbefore mounting of the measurement units 6, 8, the invention accordingto the preferred embodiment comprises a first mounting ball 18 which isattached to the housing 7 of the engine 1. A first mounting clamp 19 isadapted to be fastened on the mounting ball 18. In this regard, theposition of the first mounting clamp 19 can be adjusted and fine-tuned,and then tightened by means of a tightening screw 20. The opposite endof the first mounting clamp 19 is intended to be fastened to a firstbase bracket 21. As will be described in greater detail below, the firstbase bracket 21 acts as a support for the first measurement unit 6. Whenthe first base bracket 21 has been positioned in a correct position, itcan be locked to the first mounting clamp 19 by means of a furthertightening screw 22 in said mounting clamp 19.

[0036] In a similar manner as described above, the arrangement accordingto the preferred embodiment comprises a second mounting ball 23 which isattached to the housing 9 of the pump 2. A second mounting clamp 24 isarranged to be fastened on the second mounting ball 23. The position ofthe second mounting clamp 24 can be adjusted and fine-tuned, after whichit can be tightened by means of a tightening screw 25. The opposite endof the second mounting clamp 24 is intended to be fastened to a secondbase bracket 26. As will be described in greater detail below, thesecond base bracket 26 will act as a support for the second measurementunit 8. When the second base bracket 26 has been positioned in a correctposition, it can be locked to the second mounting clamp 24 by means of afurther tightening screw 27 in said second mounting clamp 24.

[0037] The dimensions of the mounting clamps 19, 24 may vary, and areadapted so as to allow fine-tuning of the positions of the measurementunits depending on for example the geometry of the machines. In thismanner, the actual positions of the measurement units can be adapted toeach situation in which the invention is used.

[0038]FIG. 3 indicates the manner in which the first measurement unit 6is mounted in its corresponding first base bracket 21. The firstmeasurement unit 6 is attached to a first support unit 28 which in turnis provided with a generally cone-shaped mounting member 29. Thismounting member 29 is shaped so as to be fitted into a correspondinglyshaped recess in a rotatable component 30 (see also FIG. 2) which isrotatably supported in the first base bracket 21. Furthermore, themeasurement unit 6 with its support unit 28 are fixedly mounted in therotatable compooent 30. In this manner, the first base bracket 21constitutes a support element for the relevant measurement unit, whichin turn is rotatable. The internal cone in the rotatable component 30 isconsequently rotatably arranged in the first base bracket 21. Themounting member 29 is also arranged so as to be fastened in the recessin the rotatable component 30 by means of a locking screw (not shown inFIG. 3) which is arranged to cooperate with a corresponding screw hole31 in the centre of the cone-shaped mounting member 29. In this manner,the symmetrical axis of rotation of the cone-shaped mounting member 30constitutes a fixed centre point during measurements with the invention.In particular, the entire support unit 28 (with its first measurementunit 6) can be turned about said axis of rotation so as to allowmeasurements to be provided at various rotational positions of themeasurement unit 6. Due to the arrangement with the cone-shaped mountingmember 29 and the corresponding recess, the mounting member 29 and thefirst measurement unit 6 is always correctly aligned to the centre ofthe cone-shaped recess 30.

[0039]FIG. 3 indicates the manner in which the first measurement unit 6is mounted and fine-tuned before measurements with the invention. In asimilar manner, the second measurement unit 8 is mounted by means of afurther cone-shaped mounting member arranged to be mounted in a furtherrecess 32 (see FIG. 2) provided in a further support unit.

[0040] The fastening of the support unit 28 for the first measurementunit 6 (and the fastening of a corresponding support unit for the secondmeasurement unit) does not have to be implemented by means of acone-shaped element being inserted into an internal cone. This fasteningcan be made by means of any type of mounting which secures the supportunit in fixed manner to the rotatable component 30 in the first bracket21 (and a corresponding rotatable component 32 in the second bracket26).

[0041] Consequently, both measurement units 6, 8 can be mounted in aneasy and quick manner. The type of mounting of these units 6, 8 willthen, as described above, allow rotation of the measurement units 6, 8with respect to the recesses 30, 32.

[0042] The first measurement unit 6 is electrically connected to adisplay unit 33 via a electrical cable 34. In a similar manner, thesecond measurement unit 8 is electrically connected to the display unit33 via a further electrical cable (not shown in FIG. 3). As indicatedschematically in FIG. 3, the display unit 33 is provided with a display35 which is arranged so as to present values representing the verticalangle, horizontal angle, vertical offset and horizontal offset betweenthe two shafts.

[0043] The operation of the invention will now be described in greaterdetail. The invention is arranged in a manner so as to allow the firstmeasuring unit 6 and the second measuring unit 8 to be mounted on theengine 1 and the pump 2, respectively, after which these two pieces ofmachinery are aligned in a first (or initial) state of operation, whichis preferably a cold, non-operation condition of the engine 1 and thepump 2.

[0044] As will be described below, the invention is also adapted foraligning the engine 1 and the pump 2 in a second state of operation,which is preferably a hot, operative condition of the engine 1 and thepump 2.

[0045] In the first state of operation, i.e. the cold conditionaccording to the preferred embodiment of the invention, the horizontalangle, horizontal offset, the vertical angle and vertical offset aredetermined. In particular, these measurements are carried out bycollecting an initial set of alignment readings in which the measurementunits 6, 8 are positioned in three rotational positions in therespective base brackets 21, 26. The measurement unit 6 is then movedbetween these three positions. The three positions correspond to 9o'clock, 12 o'clock and 3 o'clock according to the “clock method” orother known, suitable measurement methods. This is indicated in FIGS.4a-c, which show the manner in which the measurement units 6, 8 arerotated in relation to their brackets 21, 26 during these measurements.In each of the three positions shown in FIGS. 4a-c, measurements aremade as regards the position of the rotational axis being defined by thefirst measurement unit 6 being rotatably arranged in relation to thefirst bracket 21, and the position of the rotational axis being definedby the second measurement unit 8 being rotatably arranged in relation tothe second bracket 26. In this manner, said initial set of alignmentreadings is provided.

[0046] The results of the above-mentioned readings are programmed intothe display unit 33 and are used as a “reference” state, or “zero”setting, which consequently is related to the cold condition of themachines 1, 2. These initial readings from the display unit 33correspond to the positions of the rotational shafts being defined inthe first bracket 21 and the second bracket 26, respectively.

[0047] After measuring the errors in the cold condition, the engine 1and pump 2 are started. When the machines 1, 2 are in their hot,operating conditions, the errors are measured once again. This secondmeasurement of the errors is carried out in exactly the same manner asthe first measurement. The results of the second readings are thenstored in the display unit 33.

[0048] It should be noted that alignment readings can be collected atany time while the engine 1 is running. The measurement units 6, 8 canalso be removed between readings (provided that the brackets are kept intheir fixed positions) if this is desired.

[0049] If the initial bracket alignment readings were programmed intothe display unit 33 as targets, the results displayed on the displayunit 33 will reflect the change in the alignment condition of themachines as they progress from the cold to the hot condition.Consequently, the actual on-line changes in the alignment values can bemeasured while the machine is online under normal operating conditions.Information as regards the difference between the alignment in the coldand hot condition can thus be obtained by means of the invention.

[0050] Consequently, a first measurement is carried out in the coldcondition and a second measurement is carried out in the hot condition.The differences in position are set at “target values” for the finalshaft alignment procedure.

[0051] It can be noted that the invention constitutes a simple systemwhich can be used with generally any laser-based alignment system foraligning two components, for example of the type as described above. Bymeans of the invention, two imaginary axes (i.e. in the form of theabove-mentioned first rotational axis and second rotational axis) aredetermined when the first component and the second component are in afirst state of operation, which is normally a cold, still-standing stateof operation. In this state of operation, the relative position of thefirst component in relation to the second component is determined bydetecting the position of the first rotational axis and the secondrotational axis. As mentioned above, this can be carried out by means ofa laser alignment system comprising a first measurement unit in which alaser beam is guided to a light detector on a second measurement unit,and wherein a further laser beam (originating in said second measurementunit) is guided to a further light detector on said first measurementunit. This first measurement constitutes a reference for the cold stateof operation.

[0052] Furthermore, when the first component and the second component isin a second state of operation (normally a hot, running state ofoperation), the positions of the two imaginary axes will be changed. Inthis state of operation, the invention is operated in a manner so thatthe positions of the first rotational axis and second rotational axisare once again determined by the same alignment system and are used soas to determine the relative position of the first component in relationto the second component. The change as resulting from the fact that thecomponents being are their hot condition can then be determined. Thepositions of the first rotational axis and the second rotational axisare for example detetermined by using the “clock method”, as describedabove.

[0053] The invention is not limited to the embodiment described above;but may be varied within the scope of the appended claims. For example,the invention can be used for measuring the alignment or relativepositions between two components, in two or more distinct states ofoperations. The above-mentioned embodiment indicates two distinct statesof operations (i.e. a cold and a hot condition) but the invention can beapplied during measurements in any operational conditions, not just a“cold” and “hot” one.

[0054] With reference to the above-mentioned embodiment, in which twomachines are aligned as they progress from a cold to a hot condition, itshould be noted that alignment as they progress from a hot to a coldcondition is also possible.

[0055] Generally, the invention can be used to determine the change inthe relative position of a first component in relation to a secondcomponent. For example, the invention may thus be used for measuring theposition of a machine in relation to its support structure. Also, theinvention may be used for detecting the position of a ship engine inrelation to its hull structure. Furthermore, the invention may be usedfor determining the relative positions of different components on amachine.

1. Method for measuring the relative positions of a first component anda second component, said method comprising: mounting a first measurementunit on a housing forming part of said first component by means of afirst bracket, said first measurement unit being rotatably arranged inrelation to said first bracket and defining a first rotational axis; andmounting a second measurement unit on a further housing forming part ofsaid second component by means of a second bracket, said secondmeasurement unit being rotatably arranged in relation to said secondbracket and defining a second rotational axis; characterized in thatsaid method comprises: measuring, in a first state of operation of saidfirst component and said second component, the relative position of saidfirst component in relation to said second component by detecting theposition of said first axis and by detecting the position of said secondaxis; providing measurement values corresponding to the positions ofsaid first rotational axis and said second rotational axis, measuring,in a second state of operation of said first component and said secondcomponent, the relative position of said first component in relation tosaid second component by detecting the position of said first axis andby detecting the position of said second axis; and obtaining informationrelated to the relative positions of said first component in relation tosaid second component based on the measurements made in said first stateof operation and the measurements made in said second state ofoperation.
 2. Method according to claim 1, wherein said measurements arecarried out for a first component in the form of a machine comprising anoutput shaft and a second component in the form of a second machinecomprising an input shaft.
 3. Method according to claim 1 or 2, whereinsaid first state of operation is constituted by a cold, non-operatingcondition of said components and said second state of operation isconstituted by a hot, operating condition of said components said firstand second components being operated so that they progress from saidcold condition to said hot condition, or vice versa.
 4. Method accordingto claim 1 or 2, wherein the measurement values are obtained, in boththe first state of operation and said second state of operation, byrotating the measurement units between different positions in whichmeasurement values are registered.
 5. Method according to claim 1 or 2,wherein said measuring the relative positions in said first state ofoperation and said second state of operation is carried out by:operating a source of light on said first measurement unit, said lightbeing detected by means of a detector unit on said second measurementunit; and operating a source of light on said second measurement unit,said light being detected by means of a detector unit on said firstmeasurement unit.
 6. Method according to claim 1 or 2, wherein saidmeasuring the relative positions in said first state of operation andsaid second state of operation is carried out by: operating a source oflight on said first measurement unit, said light being reflected bymeans of a reflector unit on said second measurement unit; and detectingsaid light by means of a detector unit on said first measurement unit.7. Method according to claim 1 or 2, wherein said measuring the relativepositions in said first state of operation and said second state ofoperation is carried out by operating a mechanical dial indicator. 8.Apparatus for measurements of the relative positions of a firstcomponent and a second component by means of a first measurement unitand a second measurement unit, said apparatus comprising: a firstbracket for mounting the first measurement unit on a housing formingpart of said first component; a second bracket for mounting the secondmeasurement unit on a further housing forming part of said secondcomponent; and each measurement unit being fixedly mounted on arotatable element which is arranged in each corresponding bracket,thereby defining a first rotational axis for the first measurement unitin relation to the first bracket and a second rotational axis for thesecond measurement unit in relation to the second bracket (26);characterized in that: said measurement units are adapted for measuring,in a first state of operation of said first component and said secondcomponent, the relative positions of said first component in relation tosaid second component by detecting the position of said first axis andby detecting the position of said second axis, and that said measurementunit are adapted for measuring, in a second state of operation of saidfirst component and said second component, the relative positions ofsaid first component in relation to said second component by detectingthe position of said first axis and by detecting the position of saidsecond axis.
 9. Apparatus according to claim 8, wherein said firstcomponent is constituted by a first machine comprising an output shaftand said second component is constituted by a second machine comprisingan input shaft.
 10. Apparatus according to claim 8 or 9, wherein eachmeasurement unit is arranged so as to assume different rotationalpositions with respect to each corresponding bracket, duringmeasurements for obtaining measurement values related to the positionsof said first rotational axis and said second rotational axis. 11.Apparatus according to claim 8 or 9, wherein said first measurement unitcomprises a source of light; said second measurement unit comprises adetector for said source of light; said second second measurement unitcomprises a further source of light; and said first measurement unitcomprises a detector for said further source of light.
 12. Apparatusaccording to claim 8 or 9, wherein said first measurement unit comprisesa source of light; said second measurement unit comprises a reflectorfor said light; and said first measurement unit comprises a detector forthe light reflected on said reflector.
 13. Apparatus according to claim11, wherein said sources of light comprises laser light sources. 14.Apparatus according to claim 8 or 9, wherein said first measurement unitand said second measurement unit comprises are of the type comprising amechanical dial indicator.
 15. Apparatus according to claim 8 or 9,wherein said measurement units are adapted for communicating with adisplay unit for displaying obtained information related to themeasurements made in said first and second states of operation. 16.Apparatus according to claim 12 wherein said sources of light compriselaser light sources.